The function function has many uses. When passed no variables it can be used
to make your definition executable and allowing loops. In this example you
are prompted to enter a password until you answer correctly. This demonstrates
using empty functions to generate loops and executable definitions.
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(define program
  (function ()
    (display "Enter password (Hint its password): ")
    (define response (input))
    (if (= response "password")
      (write "Great Job!")
      (do
        (write "Im sorry. Thats incorrect!")
        (program)))))

(program)
